New System Need Ideas.

Alright as of now I have a 15" t2 on a t5001bd in a 5 cube box at 38hz. I like the way it sounds but I just want something louder. I don't want to spend all that much money. I want to go to 2 15s... but I don't know what to go to and I don't know what amp would be good. What do you guys suggest. I have a explorer and want to keep the box under say 9 cubes or so. Please tell my what you guys suggest for a LOUD system that still gets pretty low like my t2 does. Keep in mind I don't want to spend a ton. $1500 is quite a bit. Maybe another t2 and a bigger amp? what do you think. I also really like the Memphis M3s.. anyone suggest them? Thanks.
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